The present invention relates to a pressure measuring apparatus used, for example, in a liquid metal cooled reactor, and more particularly to a pressure measuring apparatus using pressure transmission media and providing with temperature compensating means.
A liquid metal used, for example, in a fast breeder has a high temperature and actively reacts with water and oil. Therefore, the pressure of the liquid metal is indirectly measured using, as pressure transmission media, NaK (alloy of sodium and potassium) and a heat-resisting inert liquid such as silicone oil, which are in the form of a liquid at room temperature.
FIG. 1 shows a conventional pressure gauge of this kind. It is divided by partitions into three, i.e. a pressure receiving portion 1, a pressure transmitting portion 2, and a pressure detecting portion 3. The pressure transmitting portion 2 is divided by a pressure transmission wall 4 into two, i.e. a capillary tube 5 on the side of the pressure receiving portion 1, which contains a liquid NaK alloy 6, and a capillary tube 7 on the side of the pressure detecting portion 3, which contains silicone oil.
A liquid metal 9, a fluid to be measured, is introduced into the pressure receiving portion 1. The pressure of the liquid metal 9 is applied to a pressure receiver 10 consisting of a diaphragm or bellows and forming the partition between the pressure receiving portion 1 and pressure transmitting portion 2. The pressure is then transmitted to the pressure detecting portion 3 via the pressure transmission media, i.e. the liquid NaK alloy 6 and silicone oil 8. The pressure transmitted to a partition 11 consisting of a diaphragm or bellows between the pressure detecting portion 3 and pressure transmitting portion 2 is converted into an electric signal in a pressure detector 12 consisting of a strain gauge attached to the partition 11. The thus converted electric signal is thereafter measured. The strain gauge may, of course, be substituted by some other pressure detector like a bourdon pressure gauge, which is provided in the pressure detecting portion 3.
In such a conventional pressure gauge, however, the volumes of the sealed NaK and silicone oil are varied with changes in the ambient temperature and the temperature of the fluid to be measured. This causes variations in pressure indications as well as measurement errors.